Review of wideband MIMO channel measurement and modeling for IMT-Advanced systems

In October 2005, the next generation mobile communication system was officially named as the International Mobile Telecommunications-Advanced (IMT-Advanced) by the ITU Radiocommunication Sector (ITU-R). Wideband multiple input and multiple output (MIMO) channel models in multiple propagation environments are fundamental for IMT-Advanced systems and such research has been initiated since 2003. The research challenges come from the fact that the wider bandwidth (20-100 MHz) and the advanced multiple antenna technology have been proposed for the IMT-Advanced system, thus leading to higher sampling rates and multiple spatial propagation channels. In this review, four aspects of wideband MIMO channel measurement and modeling are discussed: (1) radio channel measurement procedure and equipment; (2) large scale fading models; (3) small scale fading models; and (4) MIMO channel models. In particular, the large scale fading affected by the carrier frequency is investigated for urban macrocells and it shows that the higher carrier frequency results in greater loss for non-line-of-sight (NLoS) conditions in the cities of China, for which the frequency dependent factor is 32.1. Moreover, the dense and the obviously higher buildings also lead to a larger angle spread (AS) of both the angle of arrival and angle of departure in urban macrocell scenarios. The results indicate that there is the potential to explore the MIMO technique for an IMT-Advanced system with larger ASs, which would lead to the high system capacity. The progress on MIMO models is described and some methods for simplifying geometry-based stochastic channel models (GBSM) are proposed. Finally future research topics on channel measurement and modeling are identified.